Laser annealing method and laser annealing apparatus

ABSTRACT

In the present invention, At least one row of lens arrays, in which a plurality of lenses are arranged in a direction intersecting with the conveying direction of a substrate to correspond to the plurality of TFT forming areas set in a matrix on the substrate, is shifted in the direction intersecting with the conveying direction of the substrate, to thereby align the lenses in the lens array with the TFT forming areas on the substrate based on the alignment reference position. The laser beams are irradiated onto the lens array when the substrate moves and the TFT forming areas reach the underneath of the corresponding lenses of the lens array, and the laser beams are focused by the plurality of lenses to anneal the amorphous silicon film in each TFT forming area.

This application is a continuation of PCT/JP2010/058787, filed on May25, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laser annealing method for condensinglaser beams by a microlens array to anneal only a thin-film transistorforming area of an amorphous silicon film. In particular, the presentinvention relates to a laser annealing method and a laser annealingapparatus for enhancing the irradiation position accuracy of laser beamsby moving the microlens array following the movement of a substrate tobe conveyed.

2. Description of Related Art

In a conventional laser annealing method, a plurality of laser beams isformed by a microlens array, and a focal point is formed for each beam,and each focal point of the beam is transferred to and imaged on anamorphous silicon film surface side, and laser processing is performedby irradiating the beams onto the amorphous silicon film surface,thereby recrystallization the amorphous silicon film in the thin-filmtransistor (hereinafter, referred to as “TFT”) forming area (forexample, refer to Japanese Laid-open Patent Publication No.2004-311906).

However, in such a conventional laser annealing method, laser beams arefocused by the microlens array and only the amorphous silicon film in aplurality of TFT forming areas is annealed, and hence, there is anadvantage in that the use efficiency of the laser beams increases.However, there is no disclosure about; moving the microlens arrayfollowing the movement of a substrate to be conveyed while meandering,positioning each lens in the microlens array at each TFT forming area,and irradiating the laser beams. Consequently, at the time of conveyingand annealing a large substrate having a size of one meter or more onone side, when the substrate is conveyed while meandering, it can bedifficult to anneal only each TFT forming area reliably due to themechanical accuracy of a conveying mechanism.

SUMMARY OF THE INVENTION

In view of the above problems, it is an object of the present inventionto provide a laser annealing method and a laser annealing apparatus thatenhances the irradiation position accuracy of laser beams by shiftingthe microlens array following the movement of a substrate to beconveyed.

In order to achieve the above object, the laser annealing method of thepresent invention is a laser annealing method for annealing an amorphoussilicon film in each of a plurality of thin-film transistor(hereinafter, referred to as “TFT”) forming areas set in a matrix on asubstrate with a predetermined array pitch, by focusing laser beams ontothe TFT forming areas by a plurality of lenses in a lens array.According to the laser annealing method, an image on a surface of thesubstrate is captured by an imaging device while the substrate is beingconveyed in either one array direction of horizontal and verticaldirections of the TFT forming areas set in the matrix, and an alignmentreference position preset on the surface of the substrate is detectedbased on the captured image. Then at least one row of lens arrays, inwhich a plurality of lenses are arranged in a direction intersectingwith a conveying direction of the substrate to correspond to theplurality of TFT forming areas, is shifted in the direction intersectingwith the conveying direction of the substrate, to align the lenses inthe lens array with the TFT forming areas on the substrate based on thealignment reference position. The laser beams are then irradiated ontothe lens array when the substrate moves and the TFT forming area reachesthe underneath of a corresponding lens of the lens array.

According to this configuration, the image on the surface of thesubstrate is captured by the imaging device while the substrate is beingconveyed in either one array direction of horizontal and verticaldirections of the TFT forming areas set in the matrix, and the alignmentreference position preset on the surface of the substrate is detectedbased on the captured image. Then at least one row of lens arrays, inwhich the plurality of lenses are arranged in the direction intersectingwith the conveying direction of the substrate to correspond to theplurality of TFT forming areas, is shifted in the direction intersectingwith the conveying direction of the substrate, to align the lenses inthe lens array with the TFT forming areas on the substrate based on thealignment reference position. The laser beams are then irradiated ontothe lens array when the substrate moves and the TFT forming areas reachthe underneath of the corresponding lenses of the lens array, and thelaser beams are focused by the plurality of lenses to anneal theamorphous silicon film in each TFT forming area.

Moreover, the lens array has such a configuration that the lens arrayincludes a plurality of rows of lens arrays in which lenses are arrangedin parallel in the direction intersecting with the conveying directionof the substrate with a pitch of an integral multiple of two or more ofan array pitch of the TFT forming areas in the same direction, and asubsequent lens array is shifted by a predetermined dimension in aparallel arrangement direction of the plurality of lenses so as to filla gap between the respective lenses in the lens array positioned at thehead in the conveying direction of the substrate. Consequently, laserbeams are focused onto the amorphous silicon film in each TFT formingarea by the lens array having such a configuration that the lens arrayincludes a plurality of rows of lens arrays in which lenses are arrangedin parallel in the direction intersecting with the conveying directionof the substrate with a pitch of an integral multiple of two or more ofthe array pitch of the TFT forming areas in the same direction, and asubsequent lens array is shifted by a predetermined dimension in theparallel arrangement direction of the plurality of lenses so as to fillthe gap between the respective lenses in the lens array positioned atthe head in the conveying direction of the substrate.

Moreover, the substrate is a TFT substrate on which wiring lines areformed horizontally and vertically, and the TFT forming area is set at acrossing of the horizontal and vertical wiring lines, and the alignmentreference position is set at an edge of the wiring line parallel to theconveying direction of the TFT substrate. Accordingly, alignment of thelenses in the lens array with the TFT forming areas on the TFT substrateis performed based on the alignment reference position set at the edgeof the wiring line parallel to the conveying direction of the TFTsubstrate, on which the TFT forming area is set at the crossing of thehorizontal and vertical wiring lines.

A laser annealing apparatus according to the present invention focuseslaser beams onto a plurality of TFT forming areas set in a matrix on asubstrate with a predetermined array pitch by a plurality of lenses in alens array, and anneals an amorphous silicon film in each of the TFTforming areas. The laser annealing apparatus includes; a conveyingdevice that conveys the substrate at a certain speed in either one arraydirection of horizontal and vertical directions of the TFT forming areasset in the matrix; a laser source that irradiates the laser beams; alens array including at least one row of a plurality of condenserlenses, arranged in parallel in a direction intersecting with aconveying direction of the substrate in a plane parallel to a surface ofthe substrate to correspond to the plurality of TFT forming areas in thesame direction; an imaging device that captures an image on the surfaceof the substrate, designating a position away from a focusing positionof laser beams by the lens array by a certain distance in a directionopposite to the conveying direction of the substrate, as an imagecapturing position; an alignment device that aligns the lenses in thelens array with the TFT forming areas on the substrate by shifting thelens array in the direction intersecting with the conveying direction ofthe substrate; and a control device that controls drive of therespective components. The control device processes images sequentiallyinput from the imaging device that captures the image on the surface ofthe substrate being conveyed, to detect an alignment reference positionpreset on the surface of the substrate, causes the lenses in the lensarray to be aligned with the TFT forming areas on the substrate based onthe alignment reference position, and controls the laser source toirradiate laser beams toward the lens array when the substrate moves andthe TFT forming areas reach the underneath of the corresponding lensesin the lens array.

According to this configuration, the control device processes imagessequentially input from the imaging device that captures the image onthe surface of the substrate being conveyed, to detect the alignmentreference position preset on the surface of the substrate, controls thedrive of the alignment device to shift the lens array in the directionintersecting with the conveying direction of the substrate, causes thelenses in the lens array to be aligned with the TFT forming areas on thesubstrate based on the alignment reference position, and controls thelaser source to irradiate laser beams toward the lens array when thesubstrate is moved by the conveying device and the TFT forming areasreach the underneath of the corresponding lenses in the lens array. Thelaser beam is then focused onto the plurality of TFT forming areas setin the matrix on the substrate with the predetermined array pitch by theplurality of lenses in the lens array, and the amorphous silicon film ineach TFT forming area is annealed.

Moreover, the lens array has such a configuration that it includes aplurality of rows of lens arrays in which lenses are arranged inparallel in a direction intersecting with the conveying direction of thesubstrate with a pitch of an integral multiple of two or more of thearray pitch of the TFT forming areas in the same direction, and asubsequent lens array is shifted by a predetermined dimension in aparallel arrangement direction of the plurality of lenses so as to filla gap between respective lenses in the lens array positioned at the headin the conveying direction of the substrate. As a result, laser beamsare focused onto the plurality of TFT forming areas by the lens arrayhaving such a configuration that the lens array includes a plurality ofrows of lens arrays in which lenses are arranged in parallel in thedirection intersecting with the conveying direction of the substratewith the pitch of the integral multiple of two or more of the arraypitch of the TFT forming areas in the same direction, and the subsequentlens array is shifted by the predetermined dimension in the parallelarrangement direction of the plurality of lenses so as to fill the gapbetween respective lenses in the lens array positioned at the head inthe conveying direction of the substrate.

Moreover the substrate is a TFT substrate on which a plurality of wiringlines are formed horizontally and vertically and the TFT forming area isset at a crossing of the plurality of wiring lines, and the alignmentreference position is set at one edge of the wiring line parallel to theconveying direction of the TFT substrate. As a result, alignment of thelenses in the lens array with the TFT forming areas on the TFT substrateis performed based on the alignment reference position set at the edgeof the wiring line parallel to the conveying direction of the TFTsubstrate on which each TFT forming area is set at the crossing of thehorizontal and vertical wiring lines.

ADVANTAGEOUS EFFECTS OF THE INVENTION

According to the invention of a first or fourth aspect, the microlensarray can be moved following the movement of the substrate beingconveyed, and hence, the irradiation position accuracy of the laserbeams can be enhanced. Consequently, at the time of conveying andannealing a large substrate having a size of one meter or more on oneside, even if the substrate is conveyed while meandering, only each TFTforming area can be annealed reliably with the mechanical accuracy ofthe conveying mechanism.

Moreover, according to the invention of a second or fifth aspect, theshape of each lens in the lens array can be made large to increase anintake of laser beams, thereby enabling to increase the irradiationenergy of laser beams onto the amorphous silicon film. Consequently, theload on the laser source that irradiates the laser beams can be reduced,thereby enabling to enhance reliability of the apparatus.

Furthermore, according to the invention of a fourth or sixth aspect,while conveying the substrate, alignment of the lens with the TFTforming area can be constantly performed based on the edge of the wiringprovided on the TFT substrate of a liquid crystal display panel or anorganic EL display panel and extending continuously in the conveyingdirection of the substrate, thereby enabling to enhance the alignmentaccuracy of the lens with the TFT forming area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an embodiment of a laser annealingapparatus according to the present invention;

FIG. 2 is a plan view showing a TFT substrate to be used in the laserannealing apparatus according to the present invention;

FIG. 3 is an explanatory diagram showing one configuration example of amicrolens array constituting the laser annealing apparatus according tothe present invention, showing the position in relation to an imagingdevice;

FIG. 4 is a block diagram showing one configuration example of a controldevice constituting the laser annealing apparatus according to thepresent invention;

FIG. 5 is an explanatory diagram illustrating detection of an edge of agate line on the TFT substrate;

FIG. 6 is a flowchart illustrating a laser annealing method according tothe present invention;

FIG. 7 is an explanatory diagram illustrating a situation in which thewhole TFT forming areas on the TFT substrate are sequentiallylaser-annealed by the microlens array;

FIG. 8 is a sectional view for explaining an annealing process of theTFT forming area on the TFT substrate by the microlens array; and

FIG. 9 is a sectional view for explaining a process for etching anannealed polysilicon film according to the laser annealing method of thepresent invention, to a certain shape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is explained hereunder withreference to the accompanying drawings. FIG. 1 is a schematic diagramshowing an embodiment of a laser annealing apparatus according to thepresent invention. The laser annealing apparatus is for focusing laserbeams by a microlens array to anneal only a TFT forming area of anamorphous silicon film formed on a substrate, and includes a conveyingdevice 1, a laser source 2, a microlens array 3, an imaging device 4, analignment device 5, and a control device 6.

Here, as shown in FIG. 2, the substrate is a TFT substrate 10 on which aplurality of data lines 7 and gate lines 8 are formed horizontally andvertically, and a TFT forming area 9 is set on a gate electrode 30(refer to FIG. 8) at a crossing of the data line 7 and the gate line 8.A plurality of TFT forming areas 9 are set in a matrix with an arraypitch (width W and length L in direction of arrow A) the same as that ofpixels 11. On the TFT substrate 10, an alignment reference position isset, which becomes a reference for alignment of the TFT forming areas 9with microlenses 15 in the microlens array 3 described later, forexample, at an edge of the data line 7 parallel to the substrateconveying direction (direction of arrow A). Specifically, in the presentembodiment, the alignment reference position is set at a right edge ofthe data line 7 located at a left end toward the substrate conveyingdirection (direction of arrow A). At this time, a horizontal distancebetween the right edge of the data line 7 and the center of the TFTforming area 9 is determined by a design value.

The conveying device 1 is for mounting the TFT substrate 10 on an uppersurface thereof and conveying the TFT substrate 10 at a certain speed ineither one array direction of horizontal and vertical directions of theTFT forming areas 9, for example, in the direction of arrow A in FIG. 2.A plurality of unit stages 12 having a plurality of ejection holes forejecting gas and a plurality of suction holes for sucking gas in anupper surface thereof, is arranged parallel to the conveying directionof the TFT substrate 10 (hereinafter, referred to as the “substrateconveying direction”). The TFT substrate 10 is conveyed with both edgesthereof being supported by conveyer rollers 13, in a state with the TFTsubstrate 10 being floated on the plurality of unit stages 12 by acertain amount due to a balance between ejection and suction of the gas.

The laser source 2 is provided above the conveying device 1. The lasersource 2 is an excimer laser that irradiates laser beams 14 having awavelength of, for example, 308 nm or 353 nm with a recurrence periodof, for example, 50 Hz.

The microlens array 3 is provided on an optical path of the laser beams14 irradiated from the laser source 2. The microlens array 3 is forfocusing the laser beams 14 onto the plurality of TFT forming areas 9set on the TFT substrate 10. The microlens array 3 has such aconfiguration that for example, six lens arrays, as shown in FIG. 3A, inwhich the microlenses 15 are arranged in parallel with a pitch of anintegral multiple of two or more (shown by 2W in FIG. 3) of an arraypitch W of the severally set TFT forming areas 9, are arranged inparallel away from each other by a distance L, intersecting with thesubstrate conveying direction (direction of arrow A in FIG. 2) in aplane parallel to the TFT substrate 10. Moreover, the microlens array 3has such a configuration that the subsequent three lens arrays(hereinafter, referred to as the “second lens group 17”) are shifted bya predetermined dimension (shown by W in FIG. 3) in a parallelarrangement direction of the microlenses 15 so as to fill the gapbetween respective lenses in the three lens arrays (hereinafter,referred to as the “first lens group 16”) positioned at the head in thesubstrate conveying direction.

A specific configuration example of the microlens array 3 is such that,as shown in FIG. 3B, a plurality of microlens arrays 3 is formed on onesurface of a transparent substrate 34, and an opaque shading film 35having openings corresponding to the microlenses 15, is formed on theother surface thereof. Moreover, a long and thin aperture window 36parallel to the lens array, is formed on the shading film 35 away fromthe second lens group 17 by a certain distance in a direction oppositeto the substrate conveying direction. An N-shaped alignment mark 37 isprovided in the aperture window 36. The alignment mark 37 is forposition alignment with the TFT substrate 10, and a centerline of adiagonal fine line 37 a parallel to the substrate conveying direction ismatched with the center of the microlenses 15 in the first lens group 16or the second lens group 17, and horizontally parallel fine lines 37 bare arranged parallel to the substrate conveying direction. As a result,respective microlenses 15 in the microlens array 3 have a certainposition relation with respect to the center of the alignment mark 37.That is to say, the respective microlenses 15 have such a relation thata horizontal distance with respect to the center of the alignment mark37 in a direction orthogonal to the substrate conveying direction is nW(n is an integer equal to or larger than 1).

The imaging device 4 is provided between adjacent unit stages 12 of theconveying device 1 corresponding to the aperture window 36 of themicrolens array 3. The imaging device 4 is for capturing an image of awiring pattern formed on the surface of the TFT substrate 10 and animage of the alignment mark 37 of the microlens array 3 simultaneously,through the substrate from an underside of the TFT substrate 10,designating a position away from a focusing position of the laser beams14 by the microlens array 3 by a certain distance in a directionopposite to the substrate conveying direction, as an image capturingposition. The imaging device 4 is a line camera (line CCD) having aplurality of light receiving elements arranged linearly intersectingwith the substrate conveying direction shown by arrow A in FIG. 3. Theimaging device 4 is provided, for example, away by a distance D from alens array 17 a of the second lens group 17 in the microlens array 3,which is positioned at the head in the substrate conveying direction,such that a centerline of a major axis of a linear light receivingsurface is matched with the centerline of the alignment mark 37 of themicrolens array 3 intersecting with the substrate conveying direction.

The alignment device 5 is provided so that the microlens array 3 can bemoved in a direction intersecting with the substrate conveyingdirection. The alignment device 5 is for moving the microlens array 3such that a distance between the alignment reference position preset onthe data line 7 on the TFT substrate 10 (hereinafter, referred to as a“substrate-side alignment reference position”) and a central position ofthe diagonal fine line 37 a of the alignment mark 37 of the microlensarray 3 (hereinafter, referred to as a lens-side alignment referenceposition) becomes a predetermined value, to align each microlens 15 inthe microlens array 3 with the TFT forming area 9 on the TFT substrate10. For example, the alignment device 5 includes a stage and a motor formoving the microlens array 3 in a direction intersecting with thesubstrate conveying direction (direction of arrow A). Moreover, anothermotor for rotating the microlens array 3 within a certain angular rangecentering on an optical axis thereof may be provided.

Reference symbol 18 in FIG. 1 denotes a homogenizer that homogenizes theintensity distribution in the cross-section of laser beams 14 irradiatedfrom the laser source 2, and reference symbol 19 denotes a condenserlens that turns the laser beams 14 into parallel beams to be irradiatedonto the microlens array 3. Moreover reference symbol 20 denotes anilluminating light source for illuminating an image capturing positionof the imaging device 4.

The control device 6 is provided connected to; the conveying device 1,the laser source 2, the imaging device 4, and the alignment device 5.The control device 6 processes on a real time basis, the substratesurface and a one-dimensional image of the alignment mark 37 of themicrolens array 3 simultaneously imaged by the imaging device 4, todetect the substrate-side alignment reference position set on the dataline 7 on the TFT substrate 10 and the lens-side alignment referenceposition of the microlens array 3. The control device 6 then drives thealignment device 5 so that the distance between these alignmentreference positions becomes the predetermined value, to move themicrolens array 3 in the direction intersecting with the substrateconveying direction, and aligns each microlens 15 in the microlens array3 with the TFT forming area 9 on the TFT substrate 10. After the TFTsubstrate 10 has moved a certain distance or a certain period of timehas passed since it was detected that the edge of the gate line 8 on theTFT substrate 10 matched with the center of the alignment mark 37 basedon the image captured by the imaging device 4, when the TFT formingareas 9 reach the underneath of the corresponding lenses in themicrolens array 3, the control device 6 controls the laser source 2 tolight up for a certain period of time and irradiate laser beams 14 ontothe microlens array 3. As shown in FIG. 4, the control device 6 includesan image processing section 21, a memory 22, an arithmetic section 23, aconveying-device drive controller 24, an alignment-device drivecontroller 25, a laser-source drive controller 26, and a control section27.

Here, the image processing section 21 detects a luminance change in thealignment direction (major axis direction) of a plurality oflight-receiving elements in the imaging device 4 by processing theone-dimensional image captured by the imaging device 4 on a real timebasis, to detect the substrate-side alignment reference position set onthe data line 7 on the TFT substrate 10 and the lens-side alignmentreference position of the microlens array 3, and detects that the edgeof the gate line 8 on the TFT substrate 10 has matched with the centerof the alignment mark 37 based on the image captured by the imagingdevice 4.

The memory 22 stores; a distance D between the imaging device 4 and thelens array 17 a of the second lens group 17 in the microlens array 3,which is positioned at the head in the substrate conveying direction, adistance between the lens arrays 16 a and 17 a positioned respectivelyat the head in the substrate conveying direction of the first lens group16 and the second lens group 17 in the microlens array 3 (for example,3L in FIG. 3), an alignment reference value for aligning the TFTsubstrate 10 with the microlens array 3, and a moving distance of theTFT substrate 10 or elapsed time since detection of the edge of the gateline 8 on the TFT substrate 10 until lighting of the laser source 2.

The arithmetic section 23 calculates a misregistration amount betweenthe substrate-side alignment reference position of the TFT substrate 10and the lens-side alignment reference position of the microlens array 3detected by the image processing section 21.

The conveying-device drive controller 24 controls drive of the conveyingdevice by a constant frequency pulse so that the TFT substrate 10 isconveyed at a certain speed.

The alignment-device drive controller 25 compares the misregistrationamount between the substrate-side alignment reference position of theTFT substrate 10 and the lens-side alignment reference position of themicrolens array 3 calculated by the arithmetic section 23 with thealignment reference value read from the memory 22, and drives thealignment device 5 so that these match with each other to shift themicrolens array 3 in the direction intersecting with the substrateconveying direction.

The laser-source drive controller 26 controls lighting and extinction ofthe laser source 2. The control section 27 integrates and controls thewhole components to operate appropriately.

An operation of the laser annealing apparatus configured in such amanner will be explained next.

At first, an input device such as a ten key is operated to store in thememory 22; the distance D between the imaging device 4 and the lensarray 17 a of the second lens group 17 in the microlens array 3, whichis positioned at the head in the substrate conveying direction, thedistance between the lens arrays 16 a and 17 a positioned respectivelyat the head in the substrate conveying direction of the first lens group16 and the second lens group 17 in the microlens array 3, the alignmentreference value for aligning the TFT substrate 10 with the microlensarray 3, and the moving distance of the TFT substrate 10 or elapsed timesince detection of the edge of the gate line 8 on the TFT substrate 10until lighting of the laser source 2.

Next the TFT substrate 10 on which an amorphous silicon film is formedto cover the whole surface thereof, is mounted on an upper surface ofthe conveying device 1, so that the amorphous silicon film is upside andthe data line 7 is positioned to become parallel to the conveyingdirection.

Then when a start switch is turned on, the conveying device 1 ispulse-controlled by the conveying-device drive controller 24 to conveythe TFT substrate 10 in the direction of arrow A shown in FIG. 1 at acertain speed, in a state with the TFT substrate 10 being floated on theupper surface of the conveying device 1 by a certain amount.

Subsequently, when the TFT substrate 10 reaches a position above theimaging device 4, the imaging device 4 simultaneously captures images ofthe data lines 7 and the gate lines 8 formed on the surface of the TFTsubstrate 10 and the alignment mark 37 of the microlens array 3 throughthe TFT substrate 10. The one-dimensional images sequentially capturedand input by the imaging device 4 are processed on a real time basis bythe image processing section 21. As shown in FIG. 5, when it is detectedthat an edge 8 a of the gate line 8 on the TFT substrate 10 matches withthe center of the alignment mark 37 of the microlens array 3, the laserannealing apparatus counts the pulses of the conveying-device drivecontroller 24 based on the detection time, to start measurement of themoving distance of the TFT substrate 10, or starts to clock the elapsedtime based on the detection time.

Here, matching of the edge 8 a of the gate line 8 on the TFT substrate10 with the center of the alignment mark 37 of the microlens array 3 canbe detected, as shown in FIG. 5, by capturing the moment when thedimensions 8 b and 8 c on the right and left in the substrate conveyingdirection of the edge 8 a of the gate line 8 between the oppositeparallel fine lines 37 b of the alignment mark 37 divided by thediagonal fine line 37 a, become equal.

Hereunder, the laser annealing method of the present invention will beexplained with reference to the flowchart in FIG. 6.

At first, in step S1, a one-dimensional image captured by the imagingdevice 4 is processed on a real time basis by the image processingsection 21, to detect positions of the right edges of a plurality ofdata lines 7 in the substrate conveying direction and a central positionof the diagonal fine line 37 a of the alignment mark 37 of the microlensarray 3 (the lens-side alignment reference position) by a luminancechange in the alignment direction (major axis direction) of a pluralityof light-receiving elements in the imaging device 4. Then, a position ofthe right edge of the data line 7, for example, at the left end in thesubstrate conveying direction, is specified as the substrate-sidealignment reference position, from the detected right edges of theplurality of data lines 7.

In step S2, a misregistration amount between the specifiedsubstrate-side alignment reference position and the lens-side alignmentreference position is calculated by the arithmetic section 23, and themisregistration amount is compared with the alignment reference valuestored in the memory 22. Then the alignment device 5 is driven by thealignment-device drive controller 25 so that these match with eachother, and the microlens array 3 is shifted in the directionintersecting with the substrate conveying direction to align themicrolenses 15 with the TFT forming areas 9.

In step S3, after the TFT substrate 10 has moved a certain distance or acertain period of time has passed since it was detected that the edge 8a of the gate line 8 on the TFT substrate 10 positioned at the head inthe conveying direction matched with the center of the alignment mark37, then as shown in FIG. 7A, when one row of the TFT forming areas 9positioned at the head in the conveying direction reaches the underneathof the lens array 17 a at the head in the conveying direction of thesecond lens group 17 in the microlens array 3, the laser-source drivecontroller 26 is driven to light up the laser source 2 for a certainperiod of time to irradiate the laser beams onto the microlens array 3,and the amorphous silicon film in the TFT forming areas 9 correspondingto the second lens group 17 is annealed. Specifically, as shown in FIG.8A, the laser beams 14 are focused onto the TFT forming areas 9 on thegate electrodes 30 by the microlenses 15, to anneal the amorphoussilicon film 28 in the TFT forming areas 9. That is, due to theirradiation of the laser beams 14, the amorphous silicon film 28 in theTFT forming area 9 melts as shown in FIG. 8B, and thereafter the moltenamorphous silicon film 28 a is rapidly cooled and recrystallizedsimultaneously with extinction of the laser source 2, thereby forming apolysilicon film. At this time, the irradiation position of the laserbeams 14 by the first lens group 16 is outside a forming area of thepixels 11, which becomes a so-called blind print. In FIG. 8, referencesymbol 29 denotes a glass substrate, and 31 denotes a SiN insulatingfilm.

In step S4, the laser source 2 is driven to light up for a certainperiod of time by the laser-source drive controller 26, every time theconveying device 1 is pulse-controlled by the conveying-device drivecontroller 24 to move the TFT substrate 10 by a distance equal to thedistance 3L between the lens arrays 16 a and 17 a positionedrespectively at the head in the substrate conveying direction of thefirst lens group 16 and the second lens group 17 in the microlens array3. As a result, the whole TFT forming areas 9 set on the TFT substrate10 are sequentially annealed and polysiliconized, thereby forming apolysilicon film 32 (refer to FIG. 9). FIG. 7B shows a state in whichthe TFT substrate 10 is moved by the distance 3L from the state in FIG.7A, and the TFT forming areas 9 between the TFT forming areas 9corresponding to the second lens group 17 are annealed by the first lensgroup 16.

In the present embodiment, alignment of the microlenses 15 in themicrolens array 3 with the TFT forming areas 9 on the TFT substrate 10in step S3 is executed constantly even while the TFT substrate 10 isbeing conveyed. Consequently, even if the TFT substrate 10 is conveyedwhile oscillating from side to side, the microlenses 15 can bepositioned on the TFT forming areas 9 following the movement of thesubstrate. As a result, only the amorphous silicon film 28 in the TFTforming area 9 can be annealed reliably, to form the polysilicon film32.

When annealing of the TFT substrate 10 is finished, then after a resistmask 33 having a certain shape is formed on the polysilicon film 32 onthe gate electrode 30 as shown in FIG. 9A, the amorphous silicon film 28and the polysilicon film 32 around the resist mask 33, and the SiNinsulating film 31 formed underneath thereof are etched and removed, asshown in FIG. 9B, by a known etching technique. By removing the resistmask 33, as shown in FIG. 9 (c), the TFT substrate 10 on which thepolysilicon film 32 having a certain shape is formed on the gateelectrode 30 can be obtained. Thereafter, by forming a source electrodeand a drain electrode on the polysilicon film 32, a low-temperaturepolysilicon thin-film transistor substrate is complete.

In the above-described embodiment, there is explained a case in whichafter the TFT forming areas 9 on the TFT substrate 10, on which theamorphous silicon film 28 is formed over the whole surface thereof, areannealed and polysiliconized, an unnecessary film around the polysiliconfilm 32 in the TFT forming area 9 is etched so that the polysilicon film32 having the predetermined shape is left. However, the presentinvention is not limited thereto, and after the unnecessary film aroundthe polysilicon film 32 in the TFT forming area 9 is removed so that thepolysilicon film 32 having the predetermined shape is left, theremaining amorphous silicon film 28 can be annealed and polysiliconized.

In the above-described embodiment, there is explained a case in whichthe imaging device 4 is provided on the conveying device side, andimages of the data lines 7 and the gate lines 8 on the substrate surfaceand the alignment mark 37 of the microlens array 3 are captured from theunderside of the TFT substrate 10 through the substrate. However, thepresent invention is not limited thereto, and the imaging device 4 maybe provided above the conveying device 1, so that the images of the datalines 7 and the gate lines 8 on the substrate surface and the alignmentmark 37 of the microlens array 3 are captured from above.

Moreover, in the above-described embodiment, there is explained a casein which the microlens array 3 includes a plurality of rows of lensarrays in which the microlenses 15 are arranged in parallel in thedirection intersecting with the substrate conveying direction with apitch (2W) twice the array pitch W of the TFT forming areas in the samedirection, and a subsequent lens array is shifted by W in the parallelarrangement direction of the plurality of microlenses 15 so as to fillthe gap between the respective microlenses 15 in the lens arraypositioned at the head in the substrate conveying direction. However,the present invention is not limited thereto, and the microlens array 3may include at least one lens array in which a plurality of microlenses15 are arranged in parallel in the direction intersecting with thesubstrate conveying direction with the same pitch W as the array pitch Wof the TFT forming areas in the same direction.

Furthermore, in the above-described embodiment, there is explained acase in which the alignment device 5 shifts the microlens array 3 in thedirection intersecting with the substrate conveying direction. However,the present invention is not limited thereto, and the microlens array 3and the imaging device 4 may be integrally moved.

Furthermore, in the above-described embodiment, there is explained acase in which the microlens array 3 is formed by one lens array havingapproximately the same length as the whole width of the TFT substrate 10intersecting with the substrate conveying direction. However, thepresent invention is not limited thereto, and the microlens array 3 maybe formed approximately in the same length as the above-described widthby alternately arranging a plurality of unit lens arrays having ashorter length than the above-described width of the TFT substrate 10.In this case, one imaging device 4 may be provided, respectively,corresponding to each unit lens array.

In the above explanation, there is explained a case in which thesubstrate is the TFT substrate 10. However, the present invention is notlimited thereto, and the substrate may be a semiconductor substrate.

It should be noted that the entire contents of Japanese PatentApplication No. 2009-134181, filed on Jun. 3, 2009, on which theconvention priority is claimed is incorporated herein by reference.

It should also be understood that many modifications and variations ofthe described embodiments of the invention will occur to a person havingan ordinary skill in the art without departing from the spirit and scopeof the present invention as claimed in the appended claims.

1. A laser annealing method for annealing an amorphous silicon film ineach of a plurality of thin-film transistor (hereinafter, referred to as“TFT”) forming areas set in a matrix on a substrate with a predeterminedarray pitch, by focusing laser beams onto the TFT forming area by aplurality of lenses in a lens array, the laser annealing methodcomprising: capturing an image on a surface of the substrate by animaging device while conveying the substrate in either one arraydirection of horizontal and vertical directions of the TFT forming areasset in the matrix, and detecting an alignment reference position preseton the surface of the substrate based on the captured image; shifting atleast one row of lens arrays, in which a plurality of lenses arearranged in a direction intersecting with a conveying direction of thesubstrate to correspond to the plurality of TFT forming areas, in thedirection intersecting with the conveying direction of the substrate,and aligning the lenses in the lens array with the TFT forming areas onthe substrate based on the alignment reference position; and irradiatingthe laser beams onto the lens array when the substrate moves and the TFTforming areas reach the underneath of corresponding lenses in the lensarray.
 2. A laser annealing method according to claim 1, wherein thelens array has such a configuration that the lens array includes aplurality of rows of lens arrays in which lenses are arranged inparallel in the direction intersecting with the conveying direction ofthe substrate with a pitch of an integral multiple of two or more of anarray pitch of the TFT forming areas in the same direction, and asubsequent lens array is shifted by a predetermined dimension in aparallel arrangement direction of the plurality of lenses so as to filla gap between respective lenses in the lens array positioned at the headin the conveying direction of the substrate.
 3. A laser annealing methodaccording to claim 1, wherein the substrate is a TFT substrate on whichwiring lines are formed horizontally and vertically, and the TFT formingarea is set at a crossing of the horizontal and vertical wiring lines,and the alignment reference position is set at an edge of the wiringline parallel to the conveying direction of the TFT substrate.
 4. Alaser annealing apparatus that focuses laser beams onto a plurality ofTFT forming areas set in a matrix on a substrate with a predeterminedarray pitch by a plurality of lenses in a lens array, and anneals anamorphous silicon film in each of the TFT forming areas, the laserannealing apparatus comprising: a conveying device that conveys thesubstrate at a certain speed in either one array direction of horizontaland vertical directions of the TFT forming areas set in the matrix; alaser source that irradiates the laser beams; a lens array including atleast one row of a plurality of condenser lenses, arranged in parallelin a direction intersecting with a conveying direction of the substratein a plane parallel to a surface of the substrate to correspond to theplurality of TFT forming areas in the same direction; an imaging devicethat captures an image on the surface of the substrate, designating aposition away from a condensing position of laser beams by the lensarray by a certain distance in a direction opposite to the conveyingdirection of the substrate, as an image capturing position; an alignmentdevice that aligns the lenses in the lens array with the TFT formingareas on the substrate by shifting the lens array in the directionintersecting with the conveying direction of the substrate; and acontrol device that controls drive of the respective components, whereinthe control device processes images sequentially input from the imagingdevice that captures the image on the surface of the substrate beingconveyed, to detect an alignment reference position preset on thesurface of the substrate, causes the lenses in the lens array to bealigned with the TFT forming areas on the substrate based on thealignment reference position, and controls the laser source to irradiatelaser beams toward the lens array when the substrate moves and the TFTforming areas reach the underneath of the corresponding lenses in thelens array.
 5. A laser annealing apparatus according to claim 4, whereinthe lens array has such a configuration that the lens array includes aplurality of rows of lens arrays in which lenses are arranged inparallel in the direction intersecting with the conveying direction ofthe substrate with a pitch of an integral multiple of two or more of anarray pitch of the TFT forming areas in the same direction, and asubsequent lens array is shifted by a predetermined dimension in aparallel arrangement direction of the plurality of lenses so as to filla gap between respective lenses in the lens array positioned at the headin the conveying direction of the substrate.
 6. A laser annealingapparatus according to claim 4, wherein the substrate is a TFT substrateon which a plurality of wiring lines is formed horizontally andvertically, and the TFT forming area is set at a crossing of theplurality of wiring lines, and the alignment reference position is setat one edge of the wiring line parallel to the conveying direction ofthe TFT substrate.